1. Field of the Invention
The present invention relates to an inorganic electroluminescent device comprising an insulating layer, a method for fabricating the electroluminescent device, and an electronic device comprising the electroluminescent device. More particularly, the present invention relates to an inorganic electroluminescent device comprising a hole transport layer, a light-emitting layer, an inorganic electron transport layer and an electron injecting electrode sequentially formed on a hole injecting electrode wherein an insulating layer is formed between the electron injecting electrode and the inorganic electron transport layer, a method for fabricating the electroluminescent device, and an electronic device comprising the electroluminescent device.
2. Description of the Related Art
Electroluminescent devices refer collectively to devices that use a luminescent material to emit light when an electric field is applied to the luminescent material. Electroluminescent devices are classified into organic electroluminescent devices and inorganic electroluminescent devices depending on whether an organic material or an inorganic material is used to form a fluorescent layer.
Inorganic electroluminescent devices are devices that utilize collision of electrons that have been accelerated by a high electric field to emit light, and are subdivided into alternating-current thin-film electroluminescent devices, direct-current thick-film electroluminescent device, and the like, with regard to the thickness of the films and the operating modes of the electroluminescent devices prepared with them.
In recent years, quantum dot (also referred to herein as “nanodot”) inorganic electroluminescent devices comprising a light-emitting layer formed using quantum dots-have been used to prepare current-driven (that is, direct current-driven) thin-film electroluminescent devices. However, current-driven inorganic electroluminescent devices comprising an electron transport layer (“ETL”) made of an inorganic material can often exhibit, when electrons are injected from an electron injecting electrode into the electron transport layer, only a partial light emission limited to the edges of the electron injecting electrode, and therefore uniform light emission from the entire light-emitting surface is not achieved.
To solve these problems, attempts have been made to increase the voltage applied to devices to achieve more efficient injection of electrons. As a result of these attempts however, undesirable phenomena such as bubbling, occur between the electron injecting electrode and an adjacent electron transport layer, causing separation of the electron injecting electrode.
U.S. Patent Publication No. 2004-0135495 discloses color electroluminescent displays comprising a light-emitting layer, an electrode layer and an insulating layer formed therebetween. Further, Korean Patent Laid-open Nos. 2002-43161 and 2000-27755 disclose an inorganic thin film electroluminescent device comprising an energy barrier layer and a current control layer formed under an electrode, and an organic electroluminescent device comprising a cathode with a bilayer structure, respectively.
However, the prior art devices fail to solve the aforementioned problems. Accordingly, there is still an urgent need to develop an inorganic electroluminescent device that achieves efficient light emission from the entire light-emitting surface of the device.